Heat Exchanger - Mercury MerCruiser D2.8L D-Tronic Service Manual

CLOSED COOLING SYSTEM

Heat Exchanger

Refer to Cold Weather or Extended Storage, Draining Instructions in SECTION 1B and
Precautions in this section, BEFORE proceeding.
Testing
INTERNAL LEAK
An internal leak will cause coolant to go into the seawater system when pressure is put on
the closed cooling circuit.
1. Remove top seawater (inlet) hose from the exchanger. Do NOT drain the exchanger.
2. Pressurize the closed cooling circuit to 137 kPa (20 psi) with a radiator tester.
3. If seawater begins to flow from the fitting there is a leak.
BLOCKAGE
IMPORTANT: Seawater flows THROUGH the tubes in the exchanger. Closed cooling
coolant flows AROUND the tubes.
1. Remove end caps and inspect for any blockage in the seawater circuit (weeds, etc.).
2. Remove closed cooling circuit hoses and inspect the tubes just inside the fittings.
Because the complete heat exchanger cannot be inspected, the heat exchanger should
be replaced if blockage is suspected.
Repair
IMPORTANT: Braze with BCUP 2 rod or silver solder. Care must be taken not to melt
other joints during repair.
1. Internal leaks can be repaired by brazing shut the ends of the leaking tube. This is only
a temporary fix because usually another tube will start leaking after a short period of time
and this also causes a reduction in cooling capacity. Do NOT close more than three
tubes.
2. Fittings and drains that have been broken off the heat exchanger can be reattached by
brazing.
Page 6B-26
NOTICE
90-860074--1 FEBRUARY 2002
SERVICE MANUAL NUMBER 22